Utilization of two-stage single-pass electrofishing to estimate abundance and develop recovery-monitoring protocols for the endangered Nooksack dace (Rhinichthys cataractae) in Canada

I demonstrate the efficiency and cost-effectiveness of a two-stage sampling method for estimating abundance of Nooksack dace (Rhinichthys cataractae), an endangered minnow in Canada. This two-stage process involves single-pass sampling, followed by calibration of single-pass sampling capture efficiency using a mark-recapture method. Based on this two-stage method, my estimated abundances in the Brunette River, Bertrand Creek, Pepin Creek, and Fishtrap Creek were 2,763 fish (95% confidence intervals (CI): 1,823-4,537), 4,359 fish (95% CI: 2,499-7,991), 30 fish (95% CI: 12-136), and 0 fish, respectively. My presence-absence model demonstrated that mean water depth, mean water velocity, and level of substrate embeddedness are important habitat characteristics affecting presence of Nooksack dace in riffle habitats. To assess the long-term recovery of this species, I recommend conducting monitoring at 5-year intervals by sampling 15 to 25 sites in each stream using my two-stage method, resulting in a total annual monitoring cost of about $23,700.